The standard used by area officials to estimate the amount of rain that would fall during a so-called "100-year storm" could be up to five inches short across Harris County, according to preliminary results of a highly anticipated federal study, a finding that promises to spur sweeping changes in development regulations, floodplain maps and infrastructure projects.

Preliminary results of a National Oceanic and Atmospheric Administration analysis of decades-worth of data show that across the county the "100-year storm" — or a storm that has a 1 percent chance of occurring in any given year — has risen by three to five inches in Harris County since the last study was conducted in 2001.

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The final data will come out in May 2018, following a peer-review process.

The "100-year storm" is a crucial standard used by public officials across the country to shape regulations on new development, draw floodplain maps and design detention basins and flood control projects.

For example, in Harris County, regulations force developers to use the 100-year storm estimate to offset the impact of paving over flood-absorbent ground. Any development — subdivision, strip mall, gas station — must build a basin that holds runoff and releases it slowly so as to not increase flooding downstream, based on how much it would rain during the 100-year storm.

If the 100-year storm estimate increases, regulations would force developers to hold more water than before.

In another example, floodplain maps are drawn by modeling how rainfall would spill out of bayous, creeks and ditches in the event of a 100-year storm. If that standards goes up, the floodplains would expand, and likely mean higher insurance rates for those newly in floodplains and stricter regulations in those areas.

Harris County Flood Control District officials said Monday that the preliminary results already have prompted meetings on how to revamp the flood control strategy come May when the numbers are finalized.

Matt Zeve, director of operations at the flood control district, said the district was determining how to open up talks with FEMA about how to redraw floodplains in the county, and who would pay for what could be a multi-million dollar effort.

"Obviously, the numbers are going to go up, it's probably going to be significant," Zeve said. "Now is the time for us to start planning for how to deal with it."